Composite coated muffler and method of making the same



June l1,

E. E. Hows 3,093,208

COMPOSITE COATED MUFFLER AND METHOD OF MAKING THE SAME Filed NOV. 17, 1960 2 Sheets-Sheet 1 June 11, 1963 E. E. Howe 3,093,208

COMPOSITE COATED MUFFLER AND METHOD OF MAKING THE SAME Filed Nov. 17, 1960 2 Sheets-Sheet 2 NI. Q1 H @l w11 7%@ IN VEN TOR. 24x/Vf [A6/46' ited States Patent Ohio Filed Nov. 17, 1960, Ser. No. 69,950 9 Claims. (Cl. 181-33) This invention relates generally to a composite coated article and a method of making the same and more particularly to a porcelainized fabricated composite assembly such as an exhaust muler for an internal combustion engine.

Exhaust mulers are usually modifications of an elementary low-pass acoustical lter comprising a through tube to which closed cavities are coupled through small holes at intervals along the tube.

To be ecient as a sound silencer, an exhaust muifler must decrease the exhaust gas velocity and must also absorb the sound waves or cancel the sound waves by interference with other Waves from the same source. For example, a sound 'wave may be broken into two parts which follow different paths and meet again out of phase before leaving the muffler.

Contemporary muler constructions usually comprise a shell or can housing in which is contained a battle means forming a plurality of closed cavities and through which extends a tubular multiple path passage. The shell or can housing preferably has a volume six to eight times the piston displacement of the internal combustion engine with which the muflier may be associated. Either the baille or the tubular elements, or both, may be provided with holes.

Because of condensation which occurs within the interior of the muffler assembly, the combustion products of the exhaust gases frequently go into solution with such condensation and form acids which have a highly destructive effect on the mufller construction. For that reason, mutllers have heretofore been considered 'an expandable article of manufacture, particularly in the automotive industry where it has not been uncommon for a mufer to be replaced at frequent recurring intervals.

In order to avoid the trouble and expense of replacing mufllers, it has been proposed to provide a ceramic enamel coating for the mufller construction. As is well known, porcelain enamel is a ceramic enamel constituting a thin layer of glass fused to a metal. Such coating is particularly useful in the prevention `of corrosion and has been widely in the appliance industry for enhancing the attractiveness and appearance of fabricated articles. The hard glossy surface of porcelain enamel resists solution, corrosion and scratching. Moreover, the metal backing of a porcelainized article provides strength and resistance to damage.

In attempting to apply the art of porcelain enameling to muffler constructions, attempts have been made to coat the completely fabricated muffler apparatus. One particularly troublesome problem is the avoidance of blind spots since the effectiveness of the coating is directly related to the continuity of the coating surface on all surfaces of the muiller which are exposed to the corrosive gases and fluids.

Furthermore, the ceramic coating of a fabricated muffler assembly is complicated by the necessity of draining from the various compartments within the muiiier either the solution used for cleaning and pickling the assembly or the suspension constituting the ground coat of frit with clay in water.

Some of the specific problems rwhich are presented in connection with the porcelainizing of a muffler con- Patented June 11, 1963 struction involve the plugging of the holes formed in the bales or the tubular components within the interior of the muler shell. It is also desirable to avoid the formation of concentrated globs of material.

In attempting to meet such problems, additional drainage holes have been employed and it has also been proposed to use additional drainage tubes which are subsequently plugged before the muffler constitutes a completed article.

It is also particularly difficult to properly fuse the coating on the muffler components because of the uneven heating which occurs within the muiiler construction upon subjecting the same to a temperature sufficiently high to accomplish fusion.

It is an object of the present invention, therefore, to provide a porcelainized fabricated composite assembly which overcomes all of the deficiencies of the prior art.

Another object of the present invention is to provide `an improved porcelainized muffler construction.

Yet another object of ,the present invention is to provide an improved process of ceramic coating a composite coated article.

Still another object of the present invention is to combine a porcelainizing procedure with a welding procedure and thereby effect a novel method of fabricating composite coated articles.

Many other features, advantages and additional objects of the present invention will become manifest to those versed in the art upon making reference to the detailed description which follows and the accompanying sheets `of drawings in which a preferred structural embodiment of an exhaust muffler is illustrated and in which an exemplary form of inert-gas consumable-electrode, shieldedarc welding technique is illustrated and by means of which the advantages of the present invention may be obtained.

On the drawings:

FIGURE 1 is an exploded view of an exhaust muffler for an internal combustion engine embodying the principles of the present invention;

FIGURE 2 is a iiow chart identifying the principal steps involved in the fabrication method of the present invention, and

FIGURE 3 is a somewhat schematic View illustrating the structures and principles involved in the use of an inert-gas consumable-electrode, shielded-arc welding technique.

' As shown on the drawings:

The principles of the present invention are generally applicable to the fabrication of any composite coated article and the method of making the same; however, the principles of the present invention find a particularly useful application in connection with the manufacture of exhaust muilers for internal combustion engines.

As shown in FIGURE 1, the muffler construction of the present invention may conveniently comprise a can housing or shell shown generally at l10, in which the various baliles and tubular members may be assembled to form the completed mutller assembly. rThus, there is provided an outlet neck 11 which is assembled to a rear head 12 and is retained in firm assembly therewith by a plurality of circumferentially spaced spot welds as at 13.

A second subassembly is constituted by an outlet tube 14. The outlet tube 14 is spot welded as at 16 to a small cartridge head 17 flanged as at 17a.

Yet another subassembly is formed by a bathe 18 and a baffle 19 spaced longitudinally and firmly assembled into an assembly unit with an inlet tube 20, a return tube 21 and a tube 22. The baflles are flanged as at 18a and 19a. When assembled into the shell of a muflier, the baflles partition the interior of the shell into separate compartments or cavities to which the tubes are coupled by small holes 25 formed at intervals along the length thereof.

The various tubes and baffles 18-22 are assembled together by spot Welds on the respective ends of the subassembly as shown at 23 and 24.

Another subassembly which is associated with the subassembly 18-24 is provided by a baffle 26 flanged as at 26a to which is connected a tuning tube 27.

Y Finally, there is provided an inlet tube 28, a bent inlet neck 29 and a front head 30 all of which are connected with one another by spot welding as at 31.

In accordance with the principles of the present invention, each of the five subassemblies (which of course are exemplary insofar as muffler constructions are concerned) are individually prefabricated, for example, from sheet metal stock, as is the shell 10. After prefabricating, each respective subassembly is coated with a ceramic enamel.

The process of porcelain enameling is well known since it has developed from an early art to a full scale industry. As commonly practiced in the United States, articles fabricated from sheet metal are subjected to a cleaning and pickling process which prepares the surface vfor enameling. Thereafter a ground coat may be applied by so-called wet process which involves the application of the ground coat through dipping or sprinkling of a suspension of frit with clay in water. The ground coat may contain a small percentage of cobalt to give it irnproved adherence. The coated article is then dried and is subsequently fused by firing, for example, in a furnace at about 830 C. An additional coat, or coats, may be applied by repeating the process.

Such a process of porcelain enameling can be separately practiced with each of the subassemblies and the muflier shell as described in connection with FIGURE l. For example, each part or subassembly is separately dipped into a cleaning and pickling bath. Thereafter, a ground coat of ceramic enamel is applied by separately dipping each part or subassernbly into a suspension containing frit. The coated article or subassembly is then dried and is subsequently fired, for example, in a furnace at about 830 C.

In accordance with the principles of the present invention, there is practiced a special step between the drying and fusing steps, namely, the removal of the ground coat from a plurality of assembly related localized bonding or joint areas. For example, note that on the cartridge head 17 there is shown a plurality of coating free areas 32 on the ange 17a. Likewise, on the bafe 18 there is provided a plurality of coating-free areas 33 at the flange 18a. On the baffles 19 and 26 the coating-free areas are shown at 34 on the flanges 19a and 26a.

On the external peripheral surface of the shell 10, a corresponding plurality of areas are freed of coating as at 36. The entire inner surface of the shell remains undisturbed and likewise, the inner surfaces of the cartridge head 17 and the baflies 18, 19 and 26 remain undisturbed.

In order to remove the ground coat, a simple brushing operation may be utilized at the localized areas thereby to remove the dried ground coat at the places specified. Since each part or subassem'bly is separately fused, good heat distribution is effected and the fusing operation is greatly simplified. There are thus formed precoated parts and subassemblies. Furthermore, each individual part or subassembly may be separately inspected prior to assembly. If a bad part is detected, for example, a part which is improperly coated, it is immediately detected and a new part can be furnished, thereby precluding loss of an entire muffler.

Note also that the tubular parts such as the parts 20, 21 and 14 which are made foraminous or are provided with apertures such as the holes 25 are uniformly coated Without plugging the holes or apertures 25. Where a completely assembled mufller is subjected to a dipping operation, the holes or apertures may sometimes be closed by bridging, however, the practice of the present invention insures continuity of coating surface without filling of the holes or apertures 25 by bridging or by concentrations of coating material.

The precoated prefabricated parts or subassemblies of the muflier of the present invention may also be conveniently characterized by the formation of baille flanges 17a, 18a, 19a and 26a extending in a common direction to facilitate insertion assembly within the shell. In the exemplary construction herein described, the anges 19a and 26a of the baffles 19 and 26 are aligned interiorly adjacent the localized areas 36 of the shell 10 while the flanges 17a and 18a of the cartridge head 17 and the baffle 18 are aligned with the coating-free areas 36 spaced longitudinally therefrom. Thus, each of the coating-free areas 32, 33 and 34 is aligned with respect to the coating free-areas 36. The components are bonded in firm assembly with one another Iby spot welding.

Although the internal components of the muler assembly have coating-free areas 32, 33 and 34 and the external shell of the muffler assembly has coating-free areas 36, yet the internal surface of the shell 10 remains coated as do the internal surfaces of the flanges on the cartridge head 17 andthe baffles 18, 19 and 26. Accordingly, the coated areas constitute dielectric material which precludes the use of spot welding according to a conventional resistance welding technique. It is thus contemplated by the present invention that the -rnufiler assembly components be placed in firm assembly with one another by an inert-gas consumable-electrode, shieldedarc welding technique which is exemplified by the schematic arrangement of FIGURE 3. In FIGURE 3 there is shown a reel 40 containing a wire electrode 41 which is mechanically fed through a torch head 42 to a welding arc 43 formed between the electrode 41 and the work.

The torch head 4Z has .an annular 'recess 45 connected by means of a conduit 44 to a supply of ian inert gas. Accordingly, the arc 43 which is struck between the work (exemplified lby the shell 18 land ia flange 17a) and the electrode 41 fornrs a Weld puddle 46 which is shielded lby a stream 47 containing inert gas.

The .inert gas shielded-arc welded method is characterized by the projection of small discrete rnetal droplets 4S :axially from the end of the consumable wire electrode 41 into the weld puddle 46. 'It may be noted that the projection of the rnetal droplets 48 is with sufficient force to accelerate to a finite velocity. There i-s thus fonned an integral welded bond or joint 49 which places -adjoining layers vof metal including the shell 10 and the adjoining il-ange of either the cartridge head 17 or the baffles 1S, 19 or 26 in firm assembly. The bond or joint 49 is characterized by a button fon both sides of the work since there is good heat penetration and `added material from the consumable electrode is fed int-o` the weld puddle. Moreover, because of the remaining coating on the surface confronting .the coating-free areas, the Welded ibonds 49 are l effectively insulated and the continuity of the coating surface is preserved.

The finished article thus provided permits a muflier construction to be porcelain enameled without changing the functional design to accommodate coating. Thus, Iby following the principles of the present invention, it is Iunnecessary to provide for the addition lof holes for drainage or to make any other structural revision which might possibly change the acoustics of lthe muffler construction. Moreover, no s-ubsequent closure of temporary access openings is required, complete inspection yof every part is possible prior to assembly and improved quality control is insured.

Although minor modification-s might be suggested by those versed in the art, it should be understood that I Wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. An exhaust muffler comprising, baille means forming closed cavities having a through-tubular-multiple-path passage extending therethrough with small holes in said passage rat intervals, thereby to break sound waves which follow different paths and meet again out of phase before leaving the muffler, .a shell lforming a housing to enclose said baffle means, each of said :baffle means and said shell having a thin layer of glass fused -to the :surface thereof except for a plurality of spaced points on an external surface of said baille means and a corresponding plurality of point-s on the external surface of said shell, and a welded joint at each said set of points bonding said bafe means in firm assembly with said shell.

2. An exhaust muffler of the type comprising a shell housing and insertable baille and tube components together forming closed cavities and a multiple path through tube passage having holes iat intervals, thereby to break sound waves which follow dilfere-nt paths and meet again before leaving the muffler, said housing and said components each having a thin layer of glass fused t-o the inner and outer surfaces thereof prior to assembly, said shell and said baille components having spaced confronting support portions, the outer surf-ace of each said supponting portion being initially free lof said layer of glass and a welded joint extending through said support portions to assemble the components in irm assembly with one another without adversely affecting the layer of glass.

3. The use of porcelain enameling in the fabrication of an exhaust mufer which includes the steps of fabricating 'the baille, tube :and shell housing components Ias individual sub-assemblies out of -sheet metal, cleaning and picloling each of said components, yapplying a ground coat of a suspension including frit t-o each of said components, drying said individual components, removing said ground coat from localized spots on assembly-related portions of said components, tiring each respective component to fuse the ground coat lalt the coated areas, assembling the components to align the localized spots on the assemblyrelated components, drawing an electrical arc between a consumable wire electrode and each set -of localized aligned spots to form la weld puddle, shielding the weld puddle by a stream containing inert gas, and projecting -srnall discrete metal droplets laxially from said electrode to lill the weld puddle, whereby the pre-porcelainized components lare welded in lirm assembly with one another.

4. A porcelainized `fabricated muiller assembly comprising, a plurality of sheet form elements each formed `and shaped into a separate fabricated baffle, tube and .shell housing sub-assembly, a coating on each said sheet form element comprising :a fused porcelain enamel extending continuously over substantially all of the respective surfaces of said sheet form elements, `each o-f said elements having a plurality of coating-free localized areas at assembly-related joint areas aligned in adjoining register with one another when the sub-:assemblies are arranged in :assembled relation, land `a metal bond extending through each of said assembly-related joint tareas to place said components in tir-m assembly with one another at said localized areas.

5. 'Ihe use of an inert-gas consumable-electrode shieldedaarc welding method in the lfabrication of 4an exhaust muler which includes the steps of applying a ground coat of ceramic enamel to an exhaust muler subassembly, drying the sub-assembly, removing the ground coat at a localized area on the sub-assembly, heat -fusing the ground coat to the coated areas of the sub-assembly, repeating the foregoing steps on an assembly-related component of the exhaust muffler, assembling the related componente to align the localized areas in operative registry, and applying :a metal bond to said localized tareas via the inert-gas consumable-electrode :shielded-arc welding tech- 5 nique to place the porcelainized components in irm assembly with one another.

6. The use of an inert-gas consumable-electrode shielded-arc welding method in the fabrication of an exhaust mufer which includes the steps of applying ceramic enamel to the exposed surfaces of exhaust mulller sub-assemblies except for assembly-related localized bonding areas, assembling the sub-assemblies, and forming integral metal bonds at said bonding areas by projecting small discrete metal droplets axially from the end of a consumable wire electrode into a weld puddle formed by drawing an arc between the electrode and an adjoining localized bonding area of the assembled together sub-assemblies.

7. The use of porcelain enameling in the fabrication of an exhaust muiller which includes the steps of fabricating the baffle, tube and shell housing components of an exhaust muiller as individual sub-assemblies, applying a ground coat of ceramic enamel to each respective subassembly, drying each said coated sub-assembly, removing the coating from assembly-related localized bonding areas of each sub-assembly, fusing the coating to the sub-assemblies, assembling the components with the localized bonding areas in operative registry, and welding the localized bonding areas.

8. The use of porcelain enameling in the fabrication of an exhaust mufller which includes the steps of fabricating the baifle, tube and shell housing components of an exhaust muiller as individual sub-assemblies, applying a ground coat of ceramic enamel to each respective sub-assembly, drying each said coated sub-assembly, removing the coating from assembly-related localized bonding areas of each sub-assembly, fusing the coating to the sub-assemblies, assembling the components with the localized bonding areas in operative registry, and forming integral metal bonds at said bonding areas by projecting weld metal thereinto via an inert-gas consumable-electrode shielded-arc Awelding technique.

9. The use of porcelain enameling in the fabrication of a composite coated mulfler which includes the steps of individually prefabricating baille, tube and shell housing sub-assemblies of a composite article, applying a ground coat of ceramic enamel to each respective subassembly, removing the coating from assembly-related localized joint areas of each sub-assembly, heat fusing the coating to the sub-assemblies, assembling the cornponents with the localized joint areas in operative registry, and welding the localized joint areas.

References Cited in the file of this patent UNITED STATES PATENTS 744,495 Corse Nov. 17, 1903 2,322,488 Uecker June 22, 1943 2,354,532 Martin `July 25, 1944 2,372,712 Crawford Apr. 3, 1945 2,394,383 Hopkins Feb. 5, 1946 2,761,525 Moss Sept. 4, 1956 2,825,421 Bryant Mar. 4, l1958 2,868,950 Gage Jan. 13, 1959 2,884,693 Wagner May 5, 1959 2,975,072 Bryant et al. Mar. 14, 1961 3,036,655 Powers May 29, 1962 OTHER REFERENCES Porcelain Enamel Hot Water Tanks, The Welding Journal, periodical, January 1942, pages 21 and 22.

Steel, The Metalworking Weekly, issue of February 10, 1947, pages 92, 93, and 122.

Steel, The Metalworking Weekly, issue of lune 6, 1960, vol. 146, No. 23, pages 69 and 70.

7llzusiness Week, issue of June 11, 1960, pages 170 and 1 

1. AN EXHAUST MUFFLER COMPRISING, BAFFLE MEANS FORMING CLOSED CAVITIES HAVING A THROUGH-TUBULAR-MULTIPLE-PATH PASSAGE EXTENDING THERETHROUGH WITH SMALL HOLES IN SAID PASSAGE AT INTERVALE, THEREBY TO BREAK SOUND WAVES WHICH FOLLOW DIFFERENT PATHS AND MEET AGAIN OUT OF PHASE BEFORE LEAVING THE MUFFLER, A SHELL FORMING A HOUSING TO ENCLOSE SAID BAFFLE MEANS, EACH OF SAID BAFFLE MEANS AND SAID SHELL HAVING A THIN LAYER OF GLASS FUSED TO THE SURFACE THEREOF EXCEPT FOR A PLURALITY OF SPACED POINTS ON AN EXTERNAL SURFACE OF SAID BAFFLE MEANS AND A CORRESPONDING PLURALITY OF POINTS ON THE EXTERNAL SURFACE OF SAID SHELL, AND A 